It sounds like the Wi-Fi Alliance doesn't particularly care which one is 1, 2, and 3. They've only strongly defined 4 (n), 5 (ac), and 6 (ax). [1] It also sounds like they don't think enough devices are left in the wild of a, b, g, to worry about branding them.

The best description I've heard for 1-3 was to use roughly the consumer hardware adoption curve which was 1 (b), [briefly] 2 (a), 3 (g).

[1] https://www.wi-fi.org/discover-wi-fi